Method and apparatus for drawing and stretching a flat blank into a tubular shell



y 9,1969 F. v. BROSSEIT 3,457,761

METHOD AND APPARATUS FOR DRAWING A STRETCHING A FLAT BLANK INTO A TUBULAR ELL '2 Sheets-Sheet 1 Filed March 20, 1967 \t h f I If W INVENTOR IKE/mast;

ATTORNEY y 29, 1969 F. v. BROSSEIT 3,457,751

METHOD AND APPARATUS FOR DRAWING A STRETCHING A FLAT BLANK INTQ A TUBULAR ELL Filed March 20, 1967 2 Sheets-Sheet 2 4/ m /9, I k\\\\ m N W :1. i y j %Z J7 United States Patent METHOD AND APPARATUS FOR DRAWING AND STRETCHING A FLAT BLANK INTO A TUBULAR SHELL Fritz V. Brosseit, Kansas City, Mo., assiguor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Mar. 20, 1967, Ser. No. 624,495

Int. Cl. B21d 22/28, 28/32, 35/00 U.S. Cl. 72--325 7 Claims ABSTRACT OF THE DISCLOSURE A fiat metal blank is drawn into an elongated tubular shell by a series of successive drawing and stretching operations. During each stretching operation an annular section of the shell is engaged by a stepped die punch to stretch the material above the annular section while pushing the material below the shell toward the nose of the advancing die punch. During each intervening drawing operation, the material about the annular section is reformed and pushed toward the nose of drawing die punch.

Background of the invention At present, closed-end tubes may be fabricated by subjecting a metallic disc-shaped section of a malleable blank to a series of successive drawing operations. However, the extent of elongation of the tube is limited because each successive draw reduces the amount of material available for drawing at the end of the tube. Further, each successive draw induces stress concentrations, both tensile and compressive, which usually must be relieved by annealing. Even with such intervening annealing operations, stresses induced by subsequent draws often result in frac tures, cracks or uneven or striated drawn surfaces. These problems are particularly acute in the vicinity of the closed end, because the drawing die or punch engages the end to intensify the buildup of deleterious stress concentration. In general, with present cold drawing practices, the ratio of the thickness of the original blank to the length of draw is limited by one or more of these factors.

These drawing limitations are even more of a problem where the thickness of the original blank is relatively thin, e.g., a sheet only 30 mils thick. In the manufacture of certain articles, such as platforms incorporated in electronic devices such as planar triodes, the present practice has been to drill holes in a platform blank and then weld or braze eyelets about the holes toform housings for receiving glass beads. Wire leads are passed through the housing, and the beads are fused to bond the support leads in position to extend through the platform. It would be desirable to draw these eyelets, but the thinness of the blank precludes the use of conventional drawing processes. With conventional drawing techniques, the thin stock cannot be drawn to a sufiicient elongation without encountering tears, fractures and. unpredictable wall thicknesses of the resultant drawn eyelets.

Summary of the invention The present invention contemplates overcoming the aforementioned difficulties by subjecting a thin blank to a series of repetitive drawing steps modified, however, by biting into the drawn wall during certain of the drawing steps to stretch the material of the wall in the direction of the draw so as to provide sufficient material to be drawn into a smooth tubular wall having a-substantial elongation. More particularly, a thin blank is first drawn into a cup-shaped protuberance whereafter a punch die having a salient shoulder and a set-back nose is moved 3,457,761 Patented July 29, 1969 ice into the protuberance so that the shoulder bites into the wall and longitudinally stretches the upper section of the wall while pushing material down towards the nose of the die. The pushed-down material enables the nose to draw and elongate the protuberance into a tubular configuration. Next, a rounded nose punch die is moved into the now tubular blank to flatten and reform the ridge formed during the preceding stretch draw. As a result of the reforming of the shoulder, additional material is further pushed down into the direction of the now advancing nose of the reforming and drawing punch die. These steps may be repeated until a desired elongation is provided. With this process, a very high draw ratio is obtained without the use of expensive lubricants, special apparatus and intervening annealing steps.

In one specific application of the invention, a plurality of closely spaced draws are made in a single thin platform to form a group of elongated protuberances which are subsequently shaped and punched to form eyelet housing to receive glass or ceramic beads and wire leads. The glass beads are fused to secure the wire leads in the eyelet housing. These platforms may be used as component assemblies in the manufacture of planar triodes or other electronic and semiconductor devices.

Brief description of the drawing Other advantages will appear, and a more complete understanding of the invention will be had by a consideration of the following detailed description in conjunction with the accompanying drawing wherein:

FIG. 1 is a close sectional view illustrating a platform assembly for planar triodes having eyelets that are formed by the method and apparatus of the present invention;

FIGS. 2 and 3 are partial sectional views of a drawing die arrangement wherein a punch die is moved from the position shown in FIG. 2 to that shown in FIG. 3 to initially draw and shape a protuberance in a blank;

FIGS. 4 and 5 are partial sectional views of a drawing and stretching die mechanism wherein a stepped punch die is moved from the position shown in FIG. 4 to that shown in FIG. 5 to bite into, stretch and further draw the protuberance;

FIGS. 6 and 7 are partial sectional views of a die mechanism wherein a rounded nose punch die moves from the position shown in FIG. 6 to that shown in FIG. 7 to further draw and reform a ridge resulting from the stretch and draw operations illustrated in FIG. 5;

FIGS. 8 and 9 are partial sectional views of another stretch and draw punch die for further elongating the drawn tube; and

FIGS. 10 and 11 are partial sectional views of a forming and shearing punch die mechanism for effectuating a final shaping and shearing of an eyelet housing.

Detailed description Referring first to FIG. 1, there is depicted a platform 10 having projecting eyelets 11 formed by the practice of the present invention. Leads 12 and glass or ceramic beads 13 are mounted in the eyelets 11. The beads are subsequently fused, as illustrated by reference numeral 14, to lock leads 12 in position. These leads may be used to support and provide electrical connections to components of a planar triode. A number of closely spaced eyelets 11 may be simultaneously formed to project from the platform 10, but for purposes of illustrating the invention, it is only necessary to consider the formation of one eyelet.

Referring to FIGS. 2 and 3, a blank 16 of a ductile material such as iron, nickel, cobalt and iron, nickel, chromium alloys is loaded between a hold down 17 and a female die 18 having a cylindrical drawing bore 19, the upper extremity of which is rounded as illustrated by reference numeral 21. A punch-like drawing die 22 having a rounded nose 23 is mounted for movement into a bore 19. As illustrated in FIG. 3, movement of the drawing die 22 into the bore 19 effectuates the shaping of the blank 16 to form a cup-shaped protuberance 24. The nose 23 is bullet shaped or rounded to draw the blank over the rounded extremity 21 in a manner to minimize tearing and the setting up of stress concentrations.

In the next step of the process, a special drawing punch die is used to bite into the wall of the protuberance 24 while a drawing operation takes place. The blank 16, with a protuberance 24, is positioned on a die 27 (see FIG. 4) having a bore 28 with a curved entry to receive the protuberance 24. In this instance, a punch die 29 is provided with a reduced diameter section 31 terminating again in a slightly rounded blunt nose 32. The diameter of the punch is selected to be slightly greater than the diameter of the bore 28 minus twice the thickness of the protuberance 24. At the juncture of the punch die 29 and the reduced diameter section 31, there is formed a shoulder 33. Thejuncture may be formed at a slight angle, but the peripheral edge is still relatively sharp.

When the punch die 29 moves into the protuberance 24, as illustrated in FIG. 5, the blunt, rounded nose 32 acts to reshape the bottom of the protuberance into a flattened U-shaped configuration. As this reshaping operation is taking place, the shoulder 33 bites into the inner wall of the protuberance to impart longitudinal forces that stretch the material above the shoulder while pushin the material below the shoulder toward the advancing nose 32. Inasmuch as the protuberance is confined within the bore 28, the shoulder bites into the wall and acts to form an annular ridge 35. The advancing nose 32 draws the material into a configuration of a tubular shell 34 with a flattened U-shaped bottom as shown in FIG. 5.

Attention is now directed to FIGS. 6 and 7 for consideration' of the next step of the process wherein the tubular shell 34 will be further drawn, and the ridge 35 formed by the shoulder during the previous step will be reformed to make additional material available during the drawing operation and thereby permit a substantial elongation of the tubular shell 34 without tearing or fracture. In this drawing operation, the blank 16 is placed on a die 36 having a bore 37 with a rounded entry 38 to receive the tubular shell 34. In order to further draw and reshape the shell, a punch die 39 is provided with a rounded or bullet nose 41. The diameter of the punch die 39 is selected to be slightly greater than the inner diameter of the tubular shell 34 above the ridge 35.

As illustrated in FIG. 7, the punch die 39 moves within the tubular shell so that the nose portion 41 acts on the bottom of the shell to continue the drawing into the elongated tubular configuration. As the outer periphery of the nose 41 and outer surface of the punch die 39 engage the ridge 35, the ridge is reworked and reformed into a smooth inner wall. The material of the ridge is pushed down toward the end of the advancing punch die so that material is made available to be drawn into a further elongation of the wall of the shell 42.

Next, the blank 16 and shell 42 are subjected to an additional stretching and drawing operation as illustrated in FIGS. 8 and 9. In this instance, blank 16 is mounted on a die 43 so that the tubular shell 42 projects into a bore 44 which again is provided with a rounded entry 46. A stretching and drawing punch die 47 is mounted to move within the tubular shell 42. Again the diameter of the punch die 47 is selected to be slightly larger than the diameter of the bore 44 minus twice the wall thickness of the shell 42. The punch die 47 has a reduced section 48 which forms a shoulder 49 to again bite into the inner wall of the tubular shell 42. In this instance, a nose section 51 is rounded to reshape the bottom of the shell during the drawing operation.

When the punch 47 moves within the shell 42, as illustrated in FIG. 9, the shoulder 49 bites into the inner wall of the shell to form a ridge 52. As the ridge is being formed, the upper wall of the shell is subjected to longitudinal stretching forces, while the material in the lower section of the shell is pushed down and drawn by the nose 51 into a further elongated tubular shell 53.

In the final step ofthe illustrated embodiment of the invention, the bottom of the tubular shell 53 isreshaped and punched by the die mechanism shown in FIGS. 10 and 11. In the practice of this step, blank 16 is mounted on a die 56 having a forming cavity 57 and a bore 58. A composite punch die is provided which comprises a shank 59 rounded at its lower end 60 to terminate in a shearing projection 61, which, in turn, has a projecting rounded nose 62. When the composite punch die moves within the cavity 57 (see FIG. 11), the rounded end 60 acts on the ridge 52 and shell 53 to reform and shape the ridge and the tubular shell to conform to the configuration of cavity 57. Further, movement of the rounded nose 62 effectuates a further drawing of the shell. The advancing punch die 59 moves the shearing projection 61 to sever the bottom of the shell. The shearing action takes place between the lower extremity of the'projection 61 and the upper extremity of the wall of the bore 58. A disc 63 is severed from the bottom of theshell and passes through the bore 58 as scrap. Finally, the rounded end 60 engages the un severed bottom of the-shell 53 to squeeze and force the material into the shape of the lower portion of the die cavity, which provides an inwardly tapered lip 64. The eyelet is now completed.

In the illustrated embodiment of the invention, two stretching and drawing steps are described. It is to be understood that in other drawing operations a single stretching draw step may be used; and in still other drawing operations, where greater elongations are desired, intervening or even successive, additional stretching and drawing steps may be utilized. Further, in the illustrated embodiments separate female dies 18, 27 and 36 are shown, which may be used where the drawing and shaping steps take place ona sheet of stock material advanced through a progressive punch and die apparatus. However, it may be appreciated that the method may be practiced using a single female die in place of female dies 18, 27 and 36 in which situation the different punch dies 22, 29 and 39 may be successively moved into alignment with the female die bore and then advanced into the bore to effectuate the various forming, stretching, drawing and shaping operations.

It is to be further understood that the above-described steps and apparatus are simply illustrative of an application of the principles of the invention, and many other modifications and changes may be made without departing from the invention.

What is claimed is:

1. A method of drawing a flat blank of malleable metal into an elongated tubular configuration, which comprises: I

drawing said blank into a die cavity to form an elongated-shaped protuberance; applying longitudinal forces to an annular section of the inner wall of said protuberance to stretch the wall above the annular section to form an annunlar ridge and push the material below the annular section, while;

applying forces below said annular section to draw portions of the material pushed by the forces applied to said annular section, and applying drawing forces to said ridge to push and draw the material forming the ridge into an elongated protuberance, having a continuous smooth inner wall.

2. A method of forming a protuberance on a sheet of deformable material which comprises: H

drawing a section of said sheet of material into a concave-shaped configuration, pushing on the bottom inner surface of said concaveshaped section while biting into andadvancing an inner annular sector of said concave-shaped section to draw said concave-shaped material into a tubular configuration having an inner annular ridge, and

applying drawing forces along the inner wall of said tubular configuration to further draw the tubular material and reform the annular ridge into an elongated tubular configuration.

3. In a method of forming a substantially tubular depression in a planar body wherein a portion of the body is repetitively drawn in successive steps into a concave form of progressively increasing depth and decreasing wall thickness, the improvement which comprises:

engaging and stretching an upper wall portion of the concave form during alternate drawing steps to form an internal shoulder within the lower Wall portion, and

reforming the material of said internal shoulder during each suceeding drawing step following said stretching step to increase the depth of the drawn concave form while decreasing the wall thickness.

4. A method, as defined in claim 3, comprising the additional steps of punching a hole in the bottom of the concave form after the stretching and reforming steps are completed, and

further drawing the lower wall portion of the concave form into a downwardly and inwardly projecting taper which terminates at the periphery of the hole.

5. A method of producing an elongated, tubular eyelet in a sheet of malleable material, comprising the steps of:

drawing protuberance in the surface of the sheet of malleable material,

engaging the inner wall of said protuberance to stretch the material and form a first annular ridge while drawing the bottom of said protuberance into an elongated shell,

drawing said shell while at the same time reworking said first annular ridge to force the material into the direction of said draw,

engaging the inner Wall of said drawn shell to stretch the material to form a second annular ridge while further drawing the bottom of said shell into an elongated shell, and

punching a hole in the bottom of said shell while at the same time reworking and shaping said second annular ridge and shell to form a substantially smooth wall tubular eyelet.

6. In a punch and die for drawing a cup-shaped shell of a predetermined diameter:

a die having a cylindrical drawing bore of a diameter,

a cylindrical punch having a shank with a diameter which is less than said bore diameter but greater than said predetermined shell diameter,

a cylindrical drawing projection extending from the tip of said punch, said projection having diameter less than said shank diameter to form a sharp shoulder at the juncture with said shank, and

means for moving said punch and advancing said projection to draw the shell into said drawing bore whereupon entry of said sharp shoulder into said bore bites said shoulder into the inner Wall of said shell to push the material of said wall along with said advancing projection.

7. In a method of manipulating a series of punches to draw a flat blank into an elongated shell, wherein said punches include a first punch having a smooth periphery, a second punch having a reduced peripheral section to form a shoulder and a third punch having a smooth periphery and a cross-section area which is larger than the J reduced peripheral section of the second punch:

ance to impart longitudinal forces that stretch the material above the shoulder while pushing the material below the shoulder towards the advancing end of the second punch, to reshape the protuberance into a tubular shell having a ridge about the inner perimeter of the shell; engaging the ridge with the third punch to push the material of the ridge toward the nose of the advancing third punch to elongate the tubular shell.

References Cited UNITED STATES PATENTS 1,147,273 7/ 1915 Sherbondy 72-348 1,152,983 9/1915 Sherbondy 72-348 1,200,593 10/1916 Currie 72-327 1,225,915 Zerk 72-348 1,665,203 4/1928 Delf 72-327 2,150,708 3/1939 Andrews et al. I 72-338 2,157,354 5/1939 Sherman 72-377 2,287,691 6/1942 Marchou 72-377 2,748,932 6/1956 Kaul 72-377 2,859,510 11/1958 Baxa 72-325 3,365,926 1/1968 Price 72-377 FOREIGN PATENTS 466,434 10/ 1928 Germany. 594,670 9/ 1925 France.

CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant Examiner US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 H57, (61 Dated July 23") 1G6;

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